Founder of the formidable Jalisco New Generation Cartel (CJNG), Nemesio "El Mencho" Oseguera made it the most powerful in Mexico through unrestrained use of violence, not hesitating to openly defy the government.

Killed on Sunday at the age of 59 during an army operation, he was considered the last of the country's major godfathers since the arrest and imprisonment in the United States of the founders of the Sinaloa cartel, Joaquin "El Chapo" Guzman and Ismael "Mayo" Zambada.

Washington had put a $15 million bounty on his head.

The criminal, "violent by nature" according to drug trafficking specialist José Reveles, attacked the authorities head-on, while other similar organizations remained on the defensive.

On June 20, 2020, he launched an unprecedented attack against the current Federal Secretary of Public Security, Omar García Harfuch, then head of the capital's police force, wounding him. Three people were killed, including two bodyguards.

Five years earlier, his cartel had already fired on the newly formed National Gendarmerie of Jalisco, then ambushed a convoy of police officers from that western Mexican state.

His drug traffickers then shot down a military helicopter with a rocket launcher and caused roadblocks and fires. Dozens of people were killed, including 20 police officers and nine soldiers.

Hard to see in public

Even though he appeared in 2025 at two "narcocorridos" concerts, groups singing the praises of drug traffickers, El Mencho "was very careful not to expose himself publicly, little is known about his life," Mr. Reveles told AFP.

Images of him are rare. On the US State Department's wanted poster, he appears with an angular face, impeccably combed hair and a thin mustache, while on a 1989 US Drug Enforcement Administration (DEA) card, he is seen with curly hair and coarser features.

Born in 1966 into a poor family in Michoacan, where illegal cannabis cultivation was widespread, he immigrated to the United States at a young age, where he was convicted in the 1980s for heroin trafficking. He was deported after serving his sentence.

Back in Michoacan, he joined the Cartel del Milenio, from which he was ejected following internal struggles.

"El Mencho" then left his home state for neighboring Jalisco, where in 2009 he founded the "Mata Zetas," soon renamed the Jalisco New Generation Cartel. In 2011, the gang committed one of its most symbolic massacres, leaving 35 bodies near the site of a meeting of prosecutors in Veracruz (east).

Gaining the upper hand over numerous rival gangs, the CJNG is rapidly strengthening its position. Following the extradition to the United States of "El Chapo" and "Mayo," his cartel has become the most powerful in a country where violence linked to these groups has resulted in more than 450,000 deaths and more than 100,000 disappearances since 2006.

In 2025, the U.S. State Department declared the CJNG a terrorist organization, emphasizing its "transnational nature with a presence in virtually all of Mexico." Drug trafficking, arms dealing, extortion, human trafficking, and the theft of oil and minerals—Washington accused it of a litany of crimes.

Unable to compete with its rivals who control the border with the United States, "El Mencho" infiltrates other markets.

"Europe, Asia, Africa and even Australia were less contested by Mexicans, and there drugs cost more," explains Mr. Reveles.

Oseguera was divorced and had three children. His ex-wife and two of his sons were imprisoned. She was released, while his eldest son, alias "El Menchito," received a life sentence in the United States.